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Fluid Journal : Fluid Journal 2002-2004
2 Fluid Journal Fall 1993 Percent by county 1to10 11to20 21to30 31to40 41to50 51to60 61to70 71to 80 81to90 91to100 Current conservation tillage usage as a percentage of planted cropland. kilometers 0 900 Albers conic-equal area 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 80 70 60 50 40 30 20 10 0 Percent of Cropland in Conservation Tillage Historical Data Scenario 3 Scenario 2 Scenario 1 • • • Figure 1. Historic and projected conservation tillage usage to the year 2020 for current levels of conservation tillage at 27% of cropland (scenario 1), and which increases to 57% (scenario 2) and 76% (scenario 3). minimum tillage systems are more energy efficient than conventional tillage systems. Less total energy is required to achieve approximately the same crop production under conservation-till. Organic carbon losses from the soil are reduced as are emissions by using less fossil fuel. Basis of projections This study incorporated geographic databases of conservation tillage usage and agricultural soil organic carbon with relationships of soil organic carbon dynamics. We used data from published studies to make projections of changes in organic carbon storage under three scenarios of conservation tillage use by the year 2020. The effects on fossil fuel carbon emissions were estimated from changes in fuel usage for field manipulations and herbicides. The details of how we arrived at the conclusions are too complex for this discussion but can be viewed in the full, original text cited under "References" at the end of this article. Development of the three scenarios mentioned was based on the levels of residue and the amount of cropland under conservation tillage by the year 2020. Scenario one maintains conservation tillage at current usage of about 27 percent of cropland. Scenarios two and three incrementally increase conservation tillage usage from current levels to 57 and 76 percent of planted cropland by the year 2020 (Figure 1). Calculation of carbon costs and savings is based on the estimates of energy requirements of various tillage systems in gallons of diesel fuel equivalents (DFE). These data were converted into amount of carbon per acre per year, using a typical density of No. 2 diesel fuel. Annual crop production carbon units per acre are itemized by field operation and totaled across tillage systems (Table 1).
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